Human Anatomy and Physiology Unit 4: Respiratory, Digestive, Urinary, and Reproductive Systems

Vocabulary practice flashcards covering the key structures, physiological mechanisms, hormones, and anatomical terms from the Respiratory, Digestive, Urinary, and Reproductive system chapters.

Conchae

Three mucosa-covered projections on the lateral walls of the nasal cavity that increase mucosal surface area exposed to air.

Pharynx

A muscular passageway commonly called the throat that serves as a common conduit for both food and air, divided into nasopharynx, oropharynx, and laryngopharynx.

Epiglottis

An elastic cartilage structure that blocks off the trachea from the esophagus when swallowing to prevent food from entering the lower respiratory tract.

Vocal Folds (True Vocal Cords)

Folds of mucous membrane in the larynx that vibrate when expelled air passes through them, allowing speech production.

Trachea

The rigid windpipe reinforced with C-shaped rings of hyaline cartilage that transports air toward the lungs.

Conducting Zone Structures

All respiratory passageways that transport air to and from the respiratory zone without engaging in gas exchange.

Respiratory Zone

The site of gas exchange consisting of the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Respiratory Membrane (Air-Blood Barrier)

The composite structure composed of alveolar and capillary walls through which gas exchange occurs by simple diffusion.

Tidal Volume (TV)

The normal volume of air inhaled or exhaled during quiet breathing.

Vital Capacity (VC)

The total volume of exchangeable air, calculated as the sum of tidal volume, inspiratory reserve volume ($\text{IRV}$), and expiratory reserve volume ($\text{ERV}$).

Residual Volume (RV)

The small volume of air remaining in the lungs that cannot be voluntarily expelled even after maximal forced expiration.

Bicarbonate Ion

The primary chemical form into which carbon dioxide is converted to be transported dissolved in blood plasma, serving as a critical blood pH buffer.

Alimentary Canal

A continuous coiled muscular tube, also called the gastrointestinal (GI) tract or gut, winding through the body from the mouth to the anus.

Lingual Frenulum

A fold of mucous membrane that secures the tongue to the floor of the mouth and limits its posterior movement.

Peristalsis

An involuntary propulsive mechanism involving alternating waves of contraction and relaxation of organ walls that moves food along the digestive tract.

Rugae

Large internal folds of the stomach mucosa that provide increased surface area and allow expansion.

Microvilli

Tiny projections of the plasma membrane of mucosal cells in the small intestine that harbor enzymes and increase surface area for nutrient absorption.

Enamel

The extremely hard, heavily mineralized ceramic-like substance covering the crown of a tooth that directly bears the force of chewing.

Gastrin

A hormone released by stomach cells in response to food and rising pH that stimulates the secretion of hydrochloric acid ($\text{HCl}$), mucus, and protein-digesting enzymes.

Bile

A greenish solution produced by the liver containing bile salts and phospholipids that mechanically emulsifies large fat molecules into smaller ones.

Haustral Contractions

Slow segmenting movements of the colon lasting about $1\,\text{minute}$ and occurring roughly every $30\,\text{minutes}$ to propel contents from one haustrum to the next.

Catabolism

The metabolic breakdown of complex substances into simpler molecules, releasing energy captured to synthesize adenosine triphosphate ($\text{ATP}$).

Gluconeogenesis

The metabolic process by which the liver synthesizes new glucose molecules from noncarbohydrate substances.

Low-Density Lipoproteins (LDLs)

Lipid-protein complexes that transport cholesterol and other lipids to peripheral body cells; high levels increase the risk of arterial fatty plaques.

High-Density Lipoproteins (HDLs)

Lipid-protein complexes that transport excess cholesterol from tissue cells back to the liver for disposal and excretion.

Renal Hilum

The medial indentation of the kidney through which the renal artery, renal vein, nerves, and ureter enter or exit.

Nephron

The microscopic structural and functional unit of the kidney responsible for filtering blood and producing urine.

Podocytes

Specialized epithelial cells forming the inner layer of the glomerular capsule whose intertwining extensions form filtration slits around glomerular capillaries.

Juxtamedullary Nephrons

Nephrons situated close to the cortex-medulla boundary whose long loops of Henle dip deep into the renal medulla.

Glomerular Filtration

A nonselective, passive process where systemic blood pressure forces water and dissolved solutes out of glomerular capillaries into the glomerular capsule.

Tubular Reabsorption

The process beginning in the proximal convoluted tubule where renal tubule cells reclaim needed solutes and water from filtrate and return them to peritubular capillaries.

Tubular Secretion

The movement of substances like hydrogen, potassium, and creatinine from peritubular capillaries across tubule cells into the tubular filtrate for excretion.

Trigone

The smooth, triangular region at the base of the urinary bladder outlined by the openings of the two ureters and the single urethra where infections tend to persist.

Antidiuretic Hormone (ADH)

A hormone acting on kidney collecting ducts that increases water reabsorption into the blood, preventing excessive water loss in urine.

Aldosterone

An adrenal hormone that regulates electrolyte balance by stimulating kidney tubule cells to reabsorb sodium ions, which water follows passively.

Seminiferous Tubules

Tightly coiled tubules located within the lobules of the testes where sperm production takes place.

Interstitial Cells

Endocrine cells located in the connective tissue surrounding seminiferous tubules that synthesize androgens, primarily testosterone, when stimulated by luteinizing hormone ($\text{LH}$).

Epididymis

A highly convoluted, approximately $6\,\text{m}$ long tube coiled on the posterior side of the testis where immature sperm reside for about $20\,\text{days}$ to mature and gain motility.

Ductus Deferens (Vas Deferens)

A muscular tube extending from the epididymis through the spermatic cord into the pelvis that propels sperm toward the ejaculatory duct during ejaculation.

Male Urethra

The terminal duct of the male reproductive and urinary tracts extending from the urinary bladder to the tip of the penis, divided into prostatic, membranous, and spongy (penile) regions.

Seminal Vesicles

Glands located at the base of the bladder that produce roughly $60\%$ of seminal fluid volume, secreting an alkaline fluid rich in sugar, vitamin C, and prostaglandins.

Bulbourethral Glands

Tiny, pea-sized glands producing a clear mucus that drains into the penile urethra to cleanse acidic urine traces before ejaculation and provide lubrication.

Spermatogenesis

The entire process of sperm production from stem cells (spermatogonia) through mitotic and meiotic divisions into haploid gametes within the seminiferous tubules.

Spermiogenesis

The maturational stage of spermatogenesis during which unspecialized haploid spermatids strip away excess cytoplasm and form a distinct head, midpiece, and flagellar tail.

Corpus Luteum

The endocrine structure formed from a ruptured ovarian follicle following ovulation that secretes progesterone to maintain the uterine lining.

Fimbriae

Finger-like projections on the expanded end of the fallopian tube that create fluid currents to sweep the ovulated oocyte into the uterine tube.

Endometrium

The inner mucosal lining of the uterus into which an embryo implants, whose functional layer sloughs off during menstruation if pregnancy does not occur.

Myometrium

The bulky middle layer of the uterine wall consisting of interlaced bundles of smooth muscle that rhythmically contract during labor to expel the infant.

Oogenesis

The developmental process by which female gametes (ova) are produced from oogonia through meiosis.

Secretory Phase

Days $15\text{ to }28$ of the uterine cycle, during which rising progesterone levels from the corpus luteum increase blood supply and gland activity in the endometrium to support a fertilized egg.

Areola

The pigmented, circular area of skin located slightly inferior to the center of each breast that encircles the nipple.

Inspiratory Reserve Volume (IRV)

The amount of air that can be taken in forcibly over and above the normal tidal volume.

Expiratory Reserve Volume (ERV)

The amount of air that can be forcibly exhaled after a normal tidal expiration.

Factors Affecting Respiratory Capacity

Size, sex, age, and physical condition, which collectively influence an individual's lung volumes.

Total Lung Capacity (TLC)

The maximum volume of air contained in the lungs after a maximal inspiratory effort, calculated as the sum of vital capacity ($\text{VC}$) and residual volume ($\text{RV}$).